Here are hormones that initiate fat oxidation they are Testosterone, HGH & IGF-1, Cortisol, Epinephrine, Norepinephrine and LOW Insulin levels ,

because insulin inhibits fat oxidation,
Insulin send glucose(when in excess) to adipose cells for triglyceride storage. Insulin also send Glycogen to Muscle cells.
Insulin also Initiate Protein synthesis, increases uptake of Amino Acids.

Ok now that u kno the hormones you also need to know the other factors, Every heart beat uses a couple Fatty acids. The reason Cardio is called Cardio its cuz it has alot to do with Cardiovascular system(heart, arteries and veins)
So in Order To initiate Lipolysis you need;
1- do Cardio or weight train while insulin is low. Cardio also cuases the release of epinephrine and Norepi, and of course Faster heart rate meaning more fatty acids being used. Cortisol is released after strenuous work outs, Cortisol is a very catabolic hormone so it eats away fat and muscles, and also aids in anti inflammatory and reduce pain.
Injecting synthetic testosterone blocks all Cortisol receptors this is why when cutting it preserves Muscle when dieting and doing Cardio
2- Diet needs to be with carb control as carbs initiate Insulin and Insulin inhibits fat oxidation. and carbs also lower Cortisol. And carbs also inhibit HGh release. HGH & IGF-1 helps burn fat by the means of inhibiting Insulin. This is why cutting crabs or Carb cycling works so well.

So u see there are alot of factors involved to burning that Fat.